Tutorials and Topics - Peabody Computer Music

Tutorial 25Analysis:Using the FFTAlthough the transform comes out of fft~ in the form of a signal, it is not a time-domainsignal. The only object that “understands” this special signal is the ifft~ object, whichperforms an inverse FFT on the spectrum and transforms it back into a time-domainwaveform.The signal coming out of fft~ is spectral information, not a time-domain signalWith the capture~ object you can grab some of the output of fft~ and examine thefrequency analysis of a signal.• Click on one of the ezdac~ objects to turn audio on.When audio is turned on, dspstate~ sends the MSP sampling rate out its middle outlet.We use this number to calculate a frequency that has a period of exactly 512 samples. Thisis the fundamental frequency of the FFT itself. If we send a wave of that frequency intofft~, each time slice would contain exactly one cycle of the waveform. We will actually usea cosine wave at ten times that frequency as the test tone for our analysis, as shown below.The test tone is at 10 times the base frequency of the FFT time slice196